With the increase in packaging density of electronic parts such as semiconductor chips, the mainstream of the packaging method has shifted from conventional wire bonding methods to wireless mounting methods such as flip-chip bonding methods in which a semiconductor chip is directly mounted to a circuit substrate. In the process of producing an electronic part using this mounting method, a bump is formed on a terminal electrode on a semiconductor chip on a device wafer or an external electrode for connecting to a semiconductor chip, thereby forming a metal wiring, and face down bonding the same to a substrate. Also it is common that before forming a bump, the terminal electrode is metallized to form a barrier metal layer and a bump is formed thereon.
In conventional methods of forming a bump, plating methods have been generally used. Bumps formed by a plating method are considered to be useful as an electrode because they are compact and have good electric conductivity. However, there is a concern that the formation of bumps by a plating method is insufficient for responding to miniaturization of metal wiring that is considered to develop further in the future. Thus, a method of forming a bump based on a transfer method using a transfer substrate has been proposed as in Patent Literature 1.
In the method of forming a bump with a transfer substrate, a transfer substrate in which a wiring material that will serve as a bump is previously formed on a substrate such as glass is prepared. Then the transfer substrate is put on a wafer previously metallized and the resultant is pressed and heated, thereby transferring the wiring material to the wafer to form a bump. The method can transfer any wiring material on a transfer substrate to any position of a wafer by controlling pressing and heating, and therefore enables miniaturization of metal wiring, and in addition can avoid forming wiring on a defective sector of the wafer, and can even avoid wasting resources.